Controller definition of a robotic remote center of motion

ABSTRACT

A robotic surgical system employs a surgical instrument (20), a robot (40) for navigating the surgical instrument (20) relative to an anatomical region (10) within a coordinate system (42) of the robot (40), and a robot controller (43) for defining a remote center of motion for a spherical rotation of the surgical instrument (20) within the coordinate system (42) of the robot (40) based on a physical location within the coordinate system (42) of the robot (40) of a port (12) into the anatomical region (10). The definition of the remote center of rotation is used by the robot controller (43) to command the robot (40) to align the remote center of motion of the surgical instrument (20) with the port (12) into the anatomical region (10) for spherically rotating the surgical instrument (20) relative to the port (12) into the anatomical region (10).

CROSS-REFERENCE TO PRIOR APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/470,523, filed Mar. 27, 2017, which is a continuation of U.S. Ser.No. 14/418,593, filed Jan. 30, 2015, now U.S. Pat. No. 9,603,666, issuedon Mar. 28, 2017, which is the U.S. National Phase application under 35U.S.C. § 371 of International Application No. PCT/IB2013/056336, filedon Aug. 2, 2013, which claims the benefit of U.S. Provisional PatentApplication No. 61/678,708, filed on Aug. 2, 2012. These applicationsare hereby incorporated by reference herein.

The present invention generally relates to robotic control of aspherical rotation of a surgical instrument about a fulcrum pointrelative to an anatomical port during minimally invasive surgery. Thepresent invention specifically relates to a definition by a robotcontroller of a remote center of motion for the surgical instrument atthe anatomical port during the minimally invasive surgery.

Minimally invasive surgery is performed using one or more elongatedsurgical instruments inserted into a patient's body through smallport(s). Of particular importance, a main visualization method for theminimally invasive surgery is an endoscope inserted into the patient'sbody through one of the small ports.

In robotic guided minimally invasive surgery, one or more of thesurgical instruments are held and controlled by a robotic device as thesurgical instruments are inserted through the small ports. Moreparticularly, the small ports that are placed on the patient's body arethe only incision points through which the surgical instruments may passthrough to access the inside of the patient. As such, the surgicalinstruments may rotate around these fulcrum points, but the surgicalinstrument cannot impose translational forces on the ports as this wouldcause injury and harm to the patient. This is especially important forrobotic guided surgery, because the robot has potential to exert largetranslational forces on the ports.

Some robots implement what is known as a remote center of motion (“RCM”)at a mechanical fulcrum point of a surgical instrument whereby the robotmay only enforce rotation at the small port and all translational forcesat the small port are eliminated. As known in the art, the RCM for asurgical instrument may be achieved by implementing a mechanical designof the robot that has a fixed RCM for the surgical instrument at aspecific location within a coordinate system of the robot. For example,FIG. 1 illustrates a robot 30 having an end effector 31 holding anendoscope 20. The mechanical design of robot 30, particularly endeffector 31, provides for a fixed RCM 32 for endoscope 20. During aminimally invasive surgery, RCM 32 is aligned with a small port of ananatomical region 10 of a patient within a coordinate frame 33 of robot30 as shown in FIG. 1. This alignment facilitates a spherical rotationof endoscope 20 about RCM 32 without any significant translationalforces being exerted on the small port.

For robotic devices that do not have a remote center of motion inherentin the mechanism design, a robot controller must have the capability ofdefining a virtual remote center of motion is located in space in thecoordinate frame of the robotic device and must have the capability tocalculate the necessary motions of the robot in order to position theRCM in a manner that coincides with the anatomical port while avoidingany exertion of translational forces at that point in space. Forexample, as shown in FIG. 2, a robot 40 has an end effector 41 holdingendoscope 20. Robot 40 does not have a mechanical RCM. A virtual RCM 21for endoscope 20 therefore has to be defined for endoscope 20, which isnavigated by robot 40 whereby virtual RCM 21 coincides with a port intoanatomical region 10.

To this end, the present invention provides robotic surgical systems,robot controllers and robotic surgical methods for defining a virtualRCM in the coordinate frame of a robot and for aligning the virtual RCMwith an anatomical port in an easy and non-disruptive manner.

One form of the present invention is a robotic surgical system employinga surgical instrument, a robot for navigating the surgical instrumentrelative to an anatomical region within a coordinate system of therobot, and a robot controller for defining a remote center of motion fora spherical rotation of the surgical instrument within the coordinatesystem of the robot based on a physical location within the coordinatesystem of the robot of a port into the anatomical region. The definitionof the remote center of rotation is used by the robot controller tocommand the robot to align the remote center of motion of the surgicalinstrument with the port into the anatomical region for sphericallyrotating the surgical instrument relative to the port into theanatomical region.

In various embodiments of the robotic surgical system, the robotcontroller may defines the virtual remote center of motion by using astring potentiometer attached to the robot end effector, by locating theend effector tip at the port location, by using optical shape sensingfiber attached to the robot end effector, or by using compliance controlof the robot and mathematical extraction of the remote center of motion.

A second form of the present invention includes a robotic surgicalmethod involving a definition of a remote center of motion for aspherical rotation of a surgical instrument within a coordinate systemof a robot based on a physical location within the coordinate system ofthe robot of a port into an anatomical region. The method furtherinvolves an alignment of the remote center of motion of the surgicalinstrument with the port into the anatomical region for sphericallyrotating the surgical instrument relative to the port into theanatomical region.

The foregoing forms and other forms of the present invention as well asvarious features and advantages of the present invention will becomefurther apparent from the following detailed description of variousembodiments of the present invention read in conjunction with theaccompanying drawings. The detailed description and drawings are merelyillustrative of the present invention rather than limiting, the scope ofthe present invention being defined by the appended claims andequivalents thereof.

FIG. 1 illustrates an exemplary embodiment of a mechanical remote centerof motion as known in the art.

FIG. 2 illustrates an exemplary embodiment of a virtual remote center ofmotion in accordance with the present invention.

FIG. 3 illustrates an exemplary embodiment of a robotic surgical systemin accordance with the present invention.

FIG. 4 illustrates a flowchart representative of an exemplary embodimentof a robotic surgical method in accordance with the present invention.

FIG. 5 illustrates a flowchart representative of an exemplary embodimentof a robotic surgical method in accordance with the present invention.

FIG. 6 illustrates a flowchart representative of an exemplary embodimentof a robotic surgical method in accordance with the present invention.

FIG. 7 illustrates a flowchart representative of an exemplary embodimentof a robotic surgical method in accordance with the present invention.

As shown in FIG. 3, a robotic surgical system of the present inventionemploys robot 40, a surgical instrument in the form of endoscope 20 anda robot controller 43 for any type of medical procedure including, butnot limited to, minimally invasive cardiac surgery (e.g., coronaryartery bypass grafting or mitral valve replacement), minimally invasiveabdominal surgery (laparoscopy) (e.g., prostatectomy orcholecystectomy), and natural orifice translumenal endoscopic surgery.

Robot 40 is broadly defined herein as any robotic device structurallyconfigured with motorized control of one or more joints for maneuveringan end-effector 41 as desired for the particular medical procedure. Inpractice, robot 40 may have a minimum of five (5) degrees-of-freedomincluding an end-effector translation, an end-effector axis rotation,and three (3) degrees of rotational freedom of the joints.

Endoscope 20 is broadly defined herein as any device having afield-of-view for imaging within anatomical region 10. Examples ofendoscope 20 for purposes of the present invention include, but are notlimited to, any type of scope, flexible or rigid (e.g., endoscope,arthroscope, bronchoscope, choledochoscope, colonoscope, cystoscope,duodenoscope, gastroscope, hysteroscope, laparoscope, laryngoscope,neuroscope, otoscope, push enteroscope, rhinolaryngoscope,sigmoidoscope, sinuscope, thorascope, etc.) and any device similar to ascope that is equipped with an image system (e.g., a nested cannula withimaging). The imaging is local, and surface images may be obtainedoptically with fiber optics, lenses, or miniaturized (e.g. CCD based)imaging systems.

In practice, endoscope 20 is mounted to end-effector 41 of robot 40. Apose of end-effector 41 41 of robot 40 is a position and an orientationof end-effector 41 within a coordinate system 42 of robot 40. Withendoscope 20 being inserted within anatomical region 10, any given poseof the field-of-view of endoscope 20 within the anatomical region 10corresponds to a distinct pose of end-effector 41 within the roboticcoordinate system 42. Consequently, each individual endoscopic imagegenerated by endoscope 20 within the anatomical region 10 may be linkedto a corresponding pose of endoscope 20 within the anatomical region 10.

Robot controller 43 is broadly defined herein as any controllerstructurally configured to provide commands (not shown) to robot 40 forcontrolling a pose of end-effector 41 of robot 40 as desired fornavigating endoscope 20 through a port 12 of anatomical region and forspherically rotating endoscope 20 about a virtual fulcrum point 21 upona positioning of virtual fulcrum point 21 in a manner than partially orentirely coincides with port 12. For purposes of the present invention,a spherical rotation of endoscope 20 about virtual fulcrum point 21 isbroadly defined as any rotational motion of endoscope 20 about virtualfulcrum point 21 in a fixed location of robotic coordinate system 42without any significant wobble of endoscope 20 against port 12.

In operation, robot controller 43 executes various robotic surgicalmethods of the present invention to a define a virtual remote center ofmotion for the spherical rotation endoscope 20 within robotic coordinatesystem 42 based on a physical location within robotic coordinate system42 of anatomical port 12 and to align the remote center of motion ofendoscope 20 with anatomical port 12 for spherically rotating endoscope20 relative to anatomical port 12. A description of various methodsrepresented by flowcharts shown in FIGS. 4-7 will now be describedherein to facilitate an understanding of the operation of robotcontroller 43.

A flowchart 50 as shown in FIG. 4 is representative of robotic surgicalmethod of the present invention directed to the use of a potentiometerto define the RCM for endoscope 20. Referring to FIG. 4, a stage S51 offlowchart 50 encompasses a calibration of a string potentiometer 60 thatis mounted unto end effector 41 of endoscope 40. Potentiometer 60employs a spool 61, a rotational sensor 62, a torsion spring 63, aflexible cable 64 and a coupler 65 as known in the art for providing avoltage proportional to an extension of cable 64 over a distance D. Uponbeing mounted on end effector 41, potentiometer 60 is registered inrobotic coordinate system 42 as known in the art to thereby have acalibrated location within robotic coordinate system 42 as endoscope 20is navigated via robot 20 within robotic coordinate system 42.

A stage S52 of flowchart 50 encompasses robot controller 43 calculatingthe distance D over which cable 64 has been extended to facilitate adetermination of a virtual fulcrum point 21 of endoscope 20. In oneembodiment of stage S52, cable 64 is pulled and attached via coupler 65to a desired location of virtual fulcrum point 21 along endoscope 20whereby the distance D together with the current joint positions ofrobot 40 are used conjunction with the robot kinematics by robotcontroller 43 to define the exact physical location of virtual fulcrumpoint 21 within robotic coordinate system 42. Thereafter, robotcontroller 43 commands robot 40 to navigate endoscope 20 whereby thephysical location of virtual fulcrum point 21 within robotic coordinatesystem 42 partially or entirely coincides with the physical location ofanatomical port 12 (FIG. 3) within robotic coordinate system 42.

In an alternative embodiment of stage S52, robot controller 43 commandsrobot 40 to navigate endoscope 20 whereby a desired location of virtualfulcrum point 21 within robotic coordinate system 42 partially orentirely coincides with anatomical port 12. Thereafter, cable 64 ispulled and attached via coupler 65 to the desired location of virtualfulcrum point 21 along endoscope 20 whereby the distance D together withthe current joint positions of robot 40 are used conjunction with therobot kinematics by robot controller 43 to define the exact physicallocation of virtual fulcrum point 21 within robotic coordinate system42.

A flowchart 70 as shown in FIG. 5 is representative of robotic surgicalmethod of the present invention directed to a use of locating distal tip22 (FIG. 3) of endoscope 20 at the physical location of anatomical port12. Referring to FIG. 5, a stage S71 of flowchart 70 encompasses robotcontroller 43 commanding robot 40 to navigate distal tip 22 of endoscope20 to anatomical port 12 as known in the art whereby current jointpositions of robot 40 are used conjunction with the robot kinematics byrobot controller 43 to define the exact physical location of anatomicalport 12 within robotic coordinate system 42.

Stage S72 of flowchart 70 encompasses robot controller 43 calculating adistance from anatomical port 12 to a desired virtual fulcrum point onendoscope 20. In practice, the distance D ranges from zero whereby thedesired virtual fulcrum point coincides with the physical location ofanatomical port 12 to a maximum distance between the distal tip ofendoscope 20 and the end effector of robot 40. Based on the distance Dfrom anatomical port 12 to a desired virtual fulcrum point on endoscope20, the current joint positions of robot 40 with the distal tip ofendoscope 20 at anatomical port 12 are used conjunction with the robotkinematics by robot controller 43 to define the exact physical locationof virtual fulcrum point 21 within robotic coordinate system 42. Assuch, robot controller 43 commands robot 40 to endoscope 20 relative toanatomical port 12 whereby the virtual fulcrum point partially orentirely coincides with anatomical port 12.

A flowchart 80 as shown in FIG. 6 is representative of robotic surgicalmethod of the present invention directed to the use of a shape sensingoptical fiber to define the RCM for endoscope 20. Referring to FIG. 6, astage S81 of flowchart 80 encompasses a calibration of a shape sensingoptical fiber 90 that is mounted unto end effector 41 of robot 40. Shapesensing optical fiber 90 employs Fiber Bragg Gratings 92 or otheroptical shape sensing capability within a fiber core 91 as known in theart for providing optical signals indicative of a shape of opticalfibers 90 within robotic coordinate system 42. Upon having a proximalend mounted on end effector 41, shape sensing optical fiber 90 isregistered in robotic coordinate system 42 as known in the art tothereby have a calibrated location within robotic coordinate system 42as endoscope 20 is navigated via robot 40 within robotic coordinatesystem 42.

A stage S82 of flowchart 80 encompasses robot controller 43 calculatingthe distance D between the mounted proximal end of optical fiber 90 anda distal end of optical fiber 90 to facilitate a determination of avirtual fulcrum point 21 of endoscope 20. In one embodiment of stageS82, the distal end of optical fiber 90 is coupled to a desired locationof virtual fulcrum point 21 along endoscope 20 whereby a sensed shape ofoptical fiber 90 as known in the art provides for the distance D, whichtogether with the current joint positions of robot 40 are usedconjunction with the robot kinematics by robot controller 43 to definethe exact physical location of virtual fulcrum point 21 within roboticcoordinate system 42. Thereafter, robot controller 43 commands robot 40to navigate endoscope 20 whereby the physical location of virtualfulcrum point 21 within robotic coordinate system 42 partially orentirely coincides with the physical location of anatomical port 12(FIG. 3) within robotic coordinate system 42.

In an alternative embodiment of stage S82, robot controller 43 commandsrobot 40 to navigate endoscope 40 whereby a desired location of virtualfulcrum point 21 within robotic coordinate system 42 partially orentirely coincides with anatomical port 12 (FIG. 5). Thereafter, thedistal end of optical fiber 90 is coupled to the desired location ofvirtual fulcrum point 21 along endoscope 20 whereby the distance D (FIG.4) together with the current joint positions of robot 40 are usedconjunction with the robot kinematics by robot controller 43 to definethe exact physical location of virtual fulcrum point 21 within roboticcoordinate system 42.

A flowchart 100 as shown in FIG. 7 is representative of robotic surgicalmethod of the present invention directed locating distal tip 22 ofendoscope 20 to a desired depth within anatomical region 10 to utilizecompliance control of the robot and mathematical extraction of theremote center of motion. Specifically, force and torque sensors (notshown) located on robot 40 allows robot 40 to be manually moved withlittle or no effort. The compliance control works by using the force andtorque sensors that sense the force a user exerts on the robot 40 and byusing the dynamic model of robot 40 to convert those forces and torquesinto acceleration at the joints to thereby move robot 40.

Referring to FIG. 7, a stage S101 of flowchart 100 encompasses robotcontroller 43 commanding robot 40 to navigate distal tip 22 of endoscope20 through anatomical port 11 to a desired depth as known in the art.Upon reaching the depth, the user slowly moves the robot in a mannerthat pivots endoscope 20 around the anatomical port as exemplary shownin FIG. 7. By obtaining the joint motions and calibrated positions 22a-22 c of distal tip 22 of endoscope 20 and using forward kinematicsduring this motion, robot controller 43 mathematically calculatesvirtual fulcrum point 21 during a stage S102 of flowchart 100. In oneembodiment of stage S102, the calibrated locations 22 a-22 c of distaltip 22 of endoscope 20 from time t₀ to t₃ as given by the robotkinematics is stored and their calibrated positions are used to solve anerror minimization problem that finds the point 21 that is equidistantfrom all calibrated positions 22 a-22 c.

In practice, embodiments of a potentiometer and an optical fiberalternative to the embodiments shown in FIGS. 4 and 6 may be utilized inthe implementation of a robotic surgical method of the presentinvention.

Again, in practice, robot controller 43 may be implemented by anyconfiguration of hardware, software and/or firmware for executing therobotic surgical methods of the present invention, particularly themethods shown in FIGS. 4-7.

Also, in practice, any selection of a desired virtual fulcrum point isdependent upon many factors, such as, for example, a required depth ofthe surgical instrument into the anatomical region for purposes ofperforming a surgical task and the structural configuration of thesurgical instrument relative to the anatomical structure of the patient.

From the description of FIGS. 1-7 herein, those having ordinary skill inthe art will appreciate the numerous benefits of the present inventionincluding, but not limited to, a robot controller capable of defining avirtual RCM for a surgical instrument (e.g., endoscope) mounted on anend-effector of a robot designed with or without a mechanical RCM.

Although the present invention has been described with reference toexemplary aspects, features and implementations, the disclosed systemsand methods are not limited to such exemplary aspects, features and/orimplementations. Rather, as will be readily apparent to persons skilledin the art from the description provided herein, the disclosed systemsand methods are susceptible to modifications, alterations andenhancements without departing from the spirit or scope of the presentinvention. Accordingly, the present invention expressly encompasses suchmodification, alterations and enhancements within the scope hereof.

The invention claimed is:
 1. A control unit for controlling a roboticsurgical system including a robot operably configured to navigate asurgical instrument, the control unit comprising: a robot controller,wherein the robot controller is operably configured to define a remotecenter of motion for a spherical rotation of the surgical instrument ofthe robot at a target location within the coordinate system of therobot, and wherein the robot controller is further operably configuredto command the robot to position the remote center of motion for thespherical rotation of the surgical instrument at the target location forspherically rotating the surgical instrument relative to the targetlocation.
 2. The control unit of claim 1, wherein: defining the remotecenter of motion includes a calculation of a distance from a calibratedlocation of a potentiometer within the coordinate system of the robot toa physical location of a virtual fulcrum point of the instrument withinthe coordinate system of the robot established by an attachment of thepotentiometer to an end effector of the robot and to the instrument; anddefining the remote center of motion of the instrument with a targetlocation within the region includes the physical location of the virtualfulcrum point of the instrument within the coordinate system of therobot at least partially coinciding to the physical location of thetarget location within the region within the coordinate system of therobot.
 3. The control unit of claim 1, wherein: defining the remotecenter of motion includes a calculation of a distance from a calibratedlocation of a distal tip of the instrument within the coordinate systemof the robot to a physical location of a virtual fulcrum point of theinstrument within the coordinate system of the robot; and aligning theremote center of motion of the instrument with a target location withinthe region includes the physical location of the virtual fulcrum pointof the instrument within the coordinate system of the robot at leastpartially coinciding to the physical location of the target locationwithin the region within the coordinate system of the robot.
 4. Thecontrol unit of claim 1, wherein: defining the remote center of motionincludes a calculation of distance from a calibrated location of theoptical fiber within the coordinate system of the robot to a physicallocation of a virtual fulcrum point of the instrument within thecoordinate system of the robot established by an attachment of theoptical fiber to an end effector of the robot and to the instrument; andaligning the remote center of motion of the instrument with a targetlocation within the region includes the physical location of the virtualfulcrum point of the instrument within the coordinate system of therobot at least partially coinciding to the physical location of thetarget location of the region within the coordinate system of the robot.5. The control unit of claim 1, wherein the surgical instrument is anendoscope.